Trade and Commerce
(1) Neither Parliament nor a State Legislature can pass a trade/commerce-related law that gives one state preference over another, or discriminates between states. (2) Exception: Parliament CAN do this if the law itself declares it necessary to address a genuine goods-scarcity situation somewhere in India.
This is a strong anti-discrimination rule specifically for trade legislation: no law - not even a Parliament law - can play favourites between states on trade matters, with one narrow, explicitly-justified exception for genuine scarcity emergencies (like ensuring adequate supply of an essential good during a shortage).
Parliament couldn't pass an ordinary trade law that simply favoured one state's industries over another's - but if there were a genuine scarcity of an essential commodity in one part of the country, Parliament could pass a specifically-justified law temporarily prioritising supply to the affected region.